Charge forming device



March 10, 1936. P. KOEHLY CHARGE FORMING DEVICE 2 sheets-sheet 1 FiledVNov. 9, 1951 .allA

mi J/ZM 1w /J Ham# dthnmq 2 Sheets-sheet 2 Filed Nov.. 9, 1931 PatentedMar. I10, 1936 CHARGE FO'RMING DEVICE Paul Koehly, Dayton, Ohio,assigner, by mesne assignments, to General Motors Corporation, Detroit,Mich., a corporation of Delaware Application November s, 1931, serialNo. 574,016 1 1 claims. (01261-39) l This invention relates to a chargeforming device for internal combustion engines, and is disclosed hereinas embodied in a charge forming device having a plurality of primarycarburetors 5 whichdeliver a'primary mixture of fuel and air to aplurality of secondary carburetors. in which the primary mixture may bemixed withv additional air. However, it will be understood that thepresent invention is of utility not only in connection with the type ofcharge forming device in which it is disclosed, but of generalapplication to any form of charge forming device.

It is an object of the present invention to provide means for moreaccurately proportioning the mixture on changes of temperature moreparticularly during idling and low speed operation.

It is a. further object of this invention to provide means forfacilitatingthe operation of the engine during the Warming-up period ofthe 20 engine in cold weather.

With these objects in view, the invention consists of the provision of athermostat operable ln connection with the choke device. for controllingthe opening movement of the air valve. The thermostat is so mounted thatit controls the pressure of the spring which:` holds the air valveclosed and is adapted to increase the pressure of such spring when theatmosphere surrounding the thermostat is relatively cold, so that theair valve will not open to as great a degree when the temperature is lowas when the temperature is higher, thus insuring a somewhat richermixture during operation of the engine in cold weather, or during theWarming-up period under any weather condition.

A charge forming device of the general type disclosed herein is fullyillustrated in the patent of Fred E. Aseltine et al., 1,913,741, issuedJune 13, 1933, and reference is had thereto for a full disclosure of thetimer device.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanytheopposite direction to Fig.- 1.

Fig. 5 is a detail.

The manifold which forms a part of a charge forming device of thistype`is not disclosed here- 5 in for the sake of simplifying thedisclosure, and the general construction of the carburetor is describedonly sufficiently to give a general idea of the operation of thecarburetor, this being all that is deemed necessary to understand thepres 10 ent invention.

The carburetor unit comprises a main lhousing 20, having a ange 22 .bywhich it may be attached to a corresponding flange on the manifold Fig.4 is a, fragmentary section 'viewed from in the usual manner. A valvecontrolled air inlet 15 coupling 24 is secured in position in an openingin the top of the main housing in any desirable way. A casting 26, inwhich the fuel passages are formed which convey fuel from the fuelreservoir to the nozzles, is secured to the bottom 0f 20 the mainhousing by screws or in any otherrsuitable manner, and a sheet metalfuel bowl 28 is held tight against an annular shoulder 30, formed on themain housing, by a screw 32, screwed into the casting 26. Fuel issupplied to the fuel bowl 25 from a main source of supply in theconventional manner and a constant level of fuel is maintained in thebowl by a float 33.`

A plurality of primary mixture passages 34 are formed in the bottom wallof the main hous- 30 ing and are adapted to register with correspondingpassages in the manifold when the carburetor unit is secured thereto.Communicating with the primary mixture passages through orifices 36, arethree chambers 38, which for convenience may 35 be designated fuelsupply chambers and fuel is admitteddirectly to these chambers byfuelnozzles 40 and 4I to which fuel is conveyed from the bowl 28 to conduitsnot shown herein, but fully described in the earlier application abovereferred 40 to. `A small quantity of air is admitted to these chambers38 through a slot 42 formed in apartition separating these chambers froma main air chamber 44 to which air is admitted through the coupling24`and holes 45. `This air mixes with the 45 fuel issuing from thenozzles to form a rich mixture of fuel and air which flows into theprimary mixture passages through the orifices 36 to be mixed withadditional air therein and conveyed to the secondary mixing chambers,which are formed in the manifold outlet branches, as shown in theearlier application. v

n The flow of mixture through the primary mixture passages 34 iscontrolled by a. primary throttle valve 46, which extends across all ofsaid passages and is provided with grooves 48, which register with thepassages. 'This throttle is adapted to be operated by means o f exactlythe same construction as shown in the earlier application, and whichneed not be described herein.

The air supplied to the carburetor through the coupling 24 is controlledby valve 58, normally held against the seat 52 by a spring 54 receivedbetween the valve and a flange 56 projecting from a sleeve 58, slidablymounted on a fixed sleeve 60,

vwhich is held in position in the housing in any suitable manner andguides the stem 62 to which the air valve is'secured. When the engine isnot running, the valve is held against the seat in the manner disclosedin Fig. 1 by the spring above referred to. The valve admits air directlyto the main air chamber 44 from which the air flows to the fuel supplychambers in a manner previously described, and from which airis alsoadmitted directly to the primary mixture passages 34 through diagonalair passages 63.

The chamber 44 also supplies air to the secondary mixing chambers of themanifold by means of the secondary air passage 64, which ls controlledby a manually operable air throttle valve 66, secured to a shaft 68,rotatably mounted in the main housing and by a suction operated valve10, secured to a shaft 12, which is positioned off center with respectto the passage 64 and is also rotatably mounted in the main housing. Thevalve 66 is operated by a connection extending from the operating meansof the primary throttle and the valve 1D is operated entirely by enginesuction in exactly the same manner as in the earlier application. Theseoperating ccnnections of these valves are disclosed herein, in

Fig. 3 but are not described as they have nothing to do with the presentinvention, and a detailed description would only burden the case. Inorder that the present invention may be clearly understood, it may besaid herein that the operating connections between the throttle valveand the valve 66 are so constructed that the throttle may make apredetermined movement without -any corresponding movement of the valve66, this movement being such as to permit the vehicle on which thecarburetor is used, to operate at a speed of approximately 20 miles perhour on a level before the valve 66 begins to open. Of course, nomovement of the valve 10 can take place until the valve 66 makes someopening movement.

The openingmovement of the valve 50 is ret'arded to some extent by adashpot comprising a cylinder 'I4 formed in the casting 26 and acooperating piston 16 slidable in the cylinder and secured to the lowerend of theA valve stem 62. This dashpot effects some retardation of theopening movement of the air valve following any opening movement of thethrottle for the purpose of.

preventing uttering of the valve and to assist in the formation of amixture of the desired proportions to properly operate the engine duringthe acceleration period which immediately follows any opening of ththrottle.

The devices previously described operate substantially as follows: Whenthe primary throttle is opened to any degree, the suction of the engineis admitted through the air inlet coupling 24 to form what is known as aprimary mixture and which is of properly combustible proportions andwill operate the engine without admixture of additional air inthesecondary mixing chambers. Up to the speed at which the valve 66 beginsto open,'

All of the portions of the device above defl scribed are constructed issubstantially the same manner and operated in the same way as fullydescribed in the earlier application and no further description of thedevice in general is believed necessary.

In order to facilitate starting of the engine, a'y

choke device is providedwhich comprises a lever 80 indicated in itsentirety by the reference numeral and pivoted on a pin 82, secured in aboss 83 formed integrally with and on the outer 'surface of the mainhousing 20. This lever includes an arm 84, which projects through themain housing and extends to a position beneath the flange 56. Lever 88is also provided with another arm 86 which may be termed the operatingarm and extendsupwardly, to the left and toward the carburetor outletfrom the pin 82 on the outside of the main housing, as shown in Figs. 2and 3. This operating arm is provided with a bent-over portion 88, whichis adapted to engage an adjustable stop screw 98, screwed into the wallof the main housing to determine the normal position of the choke lever,and held in adjusted position by a detent 9|. 'I'he operating arm isalso provided `with a cam 92 pivotally mounted on the arm 86 and havinga notch 93 cooperating with a lug 94 projecting from the arm 86,` sothat the cam has a limited movement with respect to the arm. A stud 95,having an oriiice 96 controlled by a set screw 91 is pivoted on the cam.Some form of operating connection,'such as a Bowden cable, is adapted tobe connected, in the orifice 9 6 and extends to some point convenient tothe operator of the vehicle so that the choke lever may be operatedmanually at any time desired. When the choke lever is operated, it isrst moved very slightly because of engagement of the cam with the stop98 to secure minute adjustments for idling. The arm'86 is then moved andlifts 'ange 56 and the sleeve 58 to hold the valve 58 closed, thuspreventing the admission of but a small quantity of air and enabling thecarburetor to supply a very rich mixture in order to facilitate startingof the engine.

It has been found by experience, that when an air valve spring isprovided which is stiff enough to hold the air Valve closed withsuicient pressure to form a mixture which is rich enough -to operate theengine at idling, or low speed operation under load, satisfactorily,when the engine is cold, that such spring holds the valve closed withsuicient pressure to cause too rich a mixture to be formed for properengine operation at idling and low speeds after the engine has becomehot, or for such operation during hot weather. To overcome thisdifficulty, the present applicant has provided a thermostat in the formof a bimetallic strip,'which is adapted to lift the flange 56 to someextent when the engine is cold, but which is adapted to move downwardlyfrom the ange as the engine becomes hot so as to relieve the pressure onthe spring and thus enable the valve 50 to be held closed with a lighterpressure after the engine is hot than in cold weather or during thewarming-up period in any Weather.

, the arm 8d. When the engine is cold, this thermostatic member occupiesthe .position shown in Fig. 5, and holds the flange 56 in a positionslightly above that which it occupies when the engine is hot, in otherwords, in the solid line position shown in Fig. of the drawings. As theengine warms, the thermostatic member assumes the position shown indotted lines in Fig. 5, permitting the flange 5% to drop until itengages the choke lever Scl itself and rests thereon. 'I'husthe warmingup of the engine causes a slight expansion of the spring 54 and reducesthe pressure with which such spring tends to hold the air valve closedand accomplishes the results above set forth.

While the form of embodiment of the present invention as hereindisclosed, constitutes a preferred form, it is to be understood thatother forms might be adopted, all coming within the scope of the claimswhich follow.

What is claimed is as follows:

l. A carburetor comprising a mixture passage, air and fuel inletstherefor, aA throttle, an air valve controlling the admission of air tothe mixture passage, a spring normally holding the air valve closed, arigid abutment against which the spring presses to determine thepressure of the spring on the valve when the engine is hot, andthermally responsive means for increasing the pressure of said spring onthe valve upon reduction of Iengine temperature.

2. A carburetor comprising a mixture passage,

air and fuel inlets therefor, a throttle, an air valve controlling theadmission of air to the mixture passage, a choke device including amember for positively holding the air valve closed and thermallyresponsive means carried by said member for l yieldingly holding the an"valve closed under certain operating conditions, said choke device beingadapted to operate the valve independently of the thermally responsivemeans.

A carburetor` comprising a mixture passage, air and fuel inletstherefor, a throttle, an air valve controlling the admission of air tothe mixture passage, a choke lever adapted to positively close the airvalve to facilitate starting and a thermostatic member having one endflxedly g secured to'said4 choke lever and adapted to yielddetermine theclosing pressure of the air valve spring under normal operatingconditions, and a thermally'responsive member carried by the choke leverand so constructed as to increase the closing pressure of the air valvespring when the engine is cold and the choke lever is in normalposition.

5. A charge forming device for internal combustion engines having incombination a primary mixture passage, a fuel inlet therefor, asecondary mixing chamber into which said primary mixture passage isadapted to deliver a primary mixture of fuel and air, a main air valvecontrolling the admission of air to both the primary mixture passageand-secondary mixing chamber, a choke lever for positively holding thevalve closed to facilitate starting when the engine is closed and forcontrolling the openingA movement of the air valve when the engine ishot, and a thermally responsive element carried by the choke. lever andso constructed as to control the opening movement of the air valve whenthe engine is cold.

6. A charge forming device for internal combustion engines having incombination a primary a choke lever adapted to be moved to close saidair valve to limit the quantity of air admitted whereby starting of theengine is facilitated and a thermally responsive member carried by saidchoke lever to control the admission of air during operation of theengine when the latter is cold, and the choke lever is in normalposition.

7. A carburetor comprising a mixture passage, air and fuel inletstherefor, a throttle, an air Valve controlling the admission of air tothe mixture passage, a choke device comprising a manu.- ally operablelever adapted to positively hold the air valve closed to facilitatestarting, and a thermally responsive element carried -by the said leverand adapted to yieldingly hold the -air valve closed under otheroperating conditions, said lever being soconstructed as to be operableto hold the valve positivelyclosed independently of the thermallyresponsive member.

8. A carburetor comprising a mixture passage, air Aand fuel inletstherefor, a throttle, an air valve controlling the admission of air-tothe mixture passage, a choke device comprising a manually operable leveradapted to positively hold the airA valve closed to facilitate starting,and a thermally responsive element having one end xedly secured to thesaid lever and adapted to yieldingly hold the air valve closed when theengine is cold and the choke lever is in normal position, said thermallyresponsive element being so constructed that it is inelfective to holdthe valve closed when the engine has become hot.

9. A carburetor comprising a mixture passage, air-and fuel inletstherefor, a throttle, an air valve controlling the admission of air tothe' mixture passage, a spring adapted to close the air valve, a chokelever adapted to positively hold the air valve closed to facilitatestarting and a thermally responsive element carried by said choke leverand adapted to increase the closing pressure on said air valve when theengine is cold i and the choke lever is in normal position, but soconstructed that it has no effect on the closing pressure of said springwhren the engine has become hot. A

10. A carburetor comprising a 'mixture passage, air and fuel inletstherefor, a throttle, a

air valve controlling said inlet, a spring normally holding the airvalve closed, a rigid abutment 'against' which the spring presses todetermine the pressure of the spring on the valve when the engine ishot, and thermally responsive means for increasing the pressure of saidspring on the valve upon reduction of engine tempera- 1n ture.

11. A carburetor comprising a mixture `passage, air and fuel inletstherefor, a throttle, a

suction operated airvalve controlling the admission of air to themixture passage, a spring opposing the opening movement of said valvethroughout its movement, a rigid abutment against which the springpresses to determine the pressure of the spring on the valve when theengine is hot, and thermally responsive means for increasing thepressure of said spring on the valve upon reduction of enginetemperature.

vPAUL KOEHLY.

